Abstract

Although paraquat has been banned in European countries, this herbicide is still used all over the world, thanks to its low-cost, high-efficiency, and fast action. Because paraquat is highly toxic to humans and animals, there is interest in mitigating the consequences of its use, namely by implementing removal procedures capable of curbing its environmental and health risks. This research describes new magnetic nanosorbents composed of magnetite cores functionalized with bio-hybrid siliceous shells, that can be used to uptake paraquat from water using magnetically-assisted procedures. The biopolymers κ-carrageenan and starch were introduced into the siliceous shells, resulting in two hybrid materials, Fe₃O₄@SiO₂/SiCRG and Fe₃O₄@SiO₂/SiStarch, respectively, that exhibit a distinct surface chemistry. The Fe₃O₄@SiO₂/SiCRG biosorbents displayed a superior paraquat removal performance, with a good fitting to the Langmuir and Toth isotherm models. The maximum adsorption capacity of paraquat for Fe₃O₄@SiO₂/SiCRG biosorbents was 257 mg·g-1, which places this sorbent among the best systems for the removal of this herbicide from water. The interesting performance of the κ-carrageenan hybrid, along with its magnetic properties and good regeneration capacity, presents a very efficient way for the remediation of water contaminated with paraquat.

Modeling of adsorption kinetics of paraquat onto Fe3O4@SiO2/SiCRG particles using pseudo 1st and 2nd order kinetic equations and the Elovich kinetic model, for an initial paraquat concentration of 90 μg/mL.